This invention relates to a level detector applicable to a radio receiver.
Generally, it is desirable for a level detector to have the following characteristics:
(i) good linearity (low distortion factor), PA1 (ii) high detection efficiency, PA1 (iii) good stability with respect to temperature variations, and PA1 (iv) a low manufacturing cost and a small size.
A transistor detector is a well-known type of high-efficiency detector.
The conventional detector using transistors performs level detection at the base emitter junction of a transistor, so that an amplified and detected output signal is obtained at the collector thereof. This kind of detector, however, is difficult to use for realizing both a good linearity characteristic a high detection efficiency due to the following reasons:
Firstly, a heavy non-linear distortion is caused by using the non-linear characteristics of the base emitter junction of the transistor.
Secondly, it is difficult to provide a load resistor, having a high resistance value, in the monolithic semiconductor chip for realizing a high detection efficiency.